1. Field of the Invention
The present invention generally relates to a graphene printed circuit pattern structure, and more specifically to a graphene printed circuit pattern structure having surface-modified nanographene platelets uniformly dispersed in a carrier resin and a filler among the nanographene platelets to enhance contact property so as to greatly increase electrical conductivity and thermal conductivity.
2. The Prior Arts
As well known, gold, silver and copper are the excellent materials for electrical conductivity. In particular, copper is the best option for the conductive wiring material in consideration of the manufacturing cost, process and endurance such that circuit boards generally employ copper foil as the electrical circuit layer. However, high quality copper foil is still costly and the manufacturers of the circuit boards have been pushed to develop other materials to replace copper foil.
Since Andre Geim and Konstantin Novoselov at the University of Manchester in the UK in 2004 successfully manufactured graphene from a piece of graphite by use of adhesive tape and were thus awarded the Nobel Prize in Physics for 2010, graphene has been widely applied to various fields due to its excellent physical properties like electrical conductivity, thermal conductivity, chemical resistance, and so on. Specifically, graphene is 0.335 nm in thickness, about only one carbon diameter, and constructed by two-dimensional crystal bonded with sp2 hybrid orbital in a form of hexagonal honeycomb. It is believed that graphene is the thinnest material in the world, and its mechanical strength is larger than steel by one hundred times more with its specific gravity only one fourth of steel. In particular, graphene is also a material with excellent thermal conductivity and electrically conductivity. Its theoretical thermal conductivity is even up to 5300 W/mK and graphene is thus an ideal material for heat dissipation.
However, one of the problems in the actual application of graphene is that graphene is easy to congregate or stack together to form a bulk. As a result, graphene is hard to be uniformly dispersed in the medium. Thus, preventing graphene sheets from stacking on each other so as to obtain graphene powder with high uniformity and less layers is the primary bottleneck for the present industries.
Electrically conductive circuits have been widely applied in many electronic industries such as micro electronic assembly and circuit substrate layout. The etching process for conductive films and the conductive slurry process are the two most commonly used schemes to manufacture the circuits on the PCB (printed circuit board). However, the etching process is complicated and possibly results in high cost and the troublesome issue of treating waste solution. As a result, the conductive slurry process has dominated the current PCB market to manufacture the electrical circuits.
In the prior arts, CN103468057A disclosed a graphene conductive ink formed by employing graphene with few stack layers, binding resin, dispersive, antifoaming agent and stabilizer. The above ingredients are well mixed by use of a dispersion apparatus and then finely ground in a grinding mill. Finally, the resultant slurry is filtered to obtain uniformly mixed graphene conductive ink. This technique needs to use graphene with a structure formed of one to three layers, which is easy to congregate and form a bulk. Actually, it is difficult to uniformly disperse graphene by only the dispersive, and the whole electrical conductivity is adversely affected.
Another CN103319954A disclosed a graphene conductive ink and a method of manufacturing the same. This patent primarily employs modified or non-modified graphene, binding resin and other additives, which are processed by high speed mixing and ultrasonic dispersion to prepare a conductive slurry. One of the drawbacks is that graphene sheets in the coating layer has poor contact property and fails to form an intact conductive network.
Additionally, WO2014070500A1 disclosed a conductive ink and a conductive coating. The conductive ink includes a conductive polymer solution comprising conductive polymer dissolved in an aqueous-based media and a mixture of carbon nanotubes and graphene oxide sheets dispersed in the conductive polymer solution. The conductive coating includes a conductive polymer and a mixture of graphene oxide sheets and carbon nanotubes dispersed in the conductive polymer. The graphene oxide sheets are easily dispersed in the queous-based media because of oxygen-containing functional groups. Specifically, the graphene oxide sheets are electrochemically reduced after the heating process at 150° C., and furthermore, carbon nanotubes and the conductive polymer are added to obtain conductive circuits. However, the graphene oxide sheets have poor electrical conductivity. While the heating process at 150° C. is performed, the graphene oxide sheets are still not fully reduced. As a result, the whole conductive property is only slightly improved,
Therefore, it is greatly needed for the graphene printed circuit pattern structure employing surface-modified nanographene platelets with specific surface property easily and uniformly dispersed in a carrier resin, and a filler uniformly placed among the surface-modified nanographene platelets to enhance effective contact for the surface-modified nanographene platelets, thereby overcoming the above problems in the prior arts.